My long term career goal is to become an independent physician scientist who focuses on drug resistance in breast cancer and combines laboratory based mechanistic research and clinical trial design and implementation. My current efforts are devoted to studying how to overcome antiestrogen resistance by modulating epithelial stromal metabolic interactions in breast cancer utilizing molecular biology techniques. My mentor Dr. Richard Pestell has expertise in breast cancer metabolism and the tumor microenvironment. My co-mentor Dr. Scott Waldman has expertise in clinical trial design and implementation. The Kimmel Cancer Center where I work is an NCI designated Cancer Center with a well-established and vibrant research program and multiple core facilities that will allow me to carry out this proposal. A career development plan based on experimental work in Dr. Pestell's lab, twice weekly interactions with Dr. Pestell, and weekly with Dr. Waldman as well as mentorship committee meetings every two months and participation in workshops and seminars is being implemented to learn technical and leadership skills. Relapsed or refractory cancer after antiestrogen therapy defines antiestrogen resistance clinically and this is a major public health issue. Antiestrogen resistance occurs in 40% of ER+ patients and it is most often fatal. We lack good biomarkers and treatments for antiestrogen resistance. It has recently been discovered that metabolic coupling with high mitochondrial metabolism in epithelial cells with low metabolism in the stroma is associated with antiestrogen resistance. We have recently demonstrated that a tumor stroma with increased reactive oxygen species (ROS), low oxidative phosphorylation metabolism (OXPHOS) and high glycolysis is found in aggressive breast cancers. This type of stromal metabolism leads to metabolic coupling and transfer of high energy catabolites to the epithelial cancer cells and is associated with antiestrogen resistance. My overall hypothesis is that metabolic coupling drives antiestrogen resistance and reversal of epithelial-stromal metabolic coupling will overcome antiestrogen resistance in breast cancer. The project aims are: i) To test the hypothesis that OXPHOS metabolic coupling is sufficient to induce antiestrogen resistance in breast cancer. I will use an in vitro stromal-epithelial cell model of estrogen receptor positive (ER+) breast cancer. I will genetically modify cells in order to generate tight epithelial-stromal metabolic coupling with epithelial cancer cells with high OXPHOS metabolism via upregulation of monocarboxylate transporter 1 (MCT1), nuclear respiration factor 1 (NRF1) and mitoNEET and stromal cells with low OXPHOS metabolism and high catabolism via upregulation of monocarboxylate transporter 4 (MCT4) and uncoupling protein 1 (UCP1) to determine if changes in the metabolism of the epithelial or stromal compartment are sufficient to increase antiestrogen resistance. These cell lines that I generate will be cultured with either fibroblasts or ER+ carcinoma cells. Antiestrogen resistance will be measured by quantifying apoptosis and proliferation of the breast cancer cells after treatment with tamoxifen and fulvestrant. We will also determine if these cell lines induce antiestrogen resistance using xenograft models. ii) To test the hypothesis that expression of genes linked to OXPHOS metabolic coupling are associated with antiestrogen resistance in a cohort of patients. I will stain a human tumor microarray (TMA) of patients with ER+ breast cancer treated with tamoxifen for the proteins listed in aim 1. I will correlate the expression of these proteins by immunohistochemistry (IHC) in the stromal and epithelial compartments with progression free survival (PFS). We will also perform gene expression profiling (GEP) of the carcinoma cells that I generate to determine if we can generate a signature that predicts antiestrogen resistance. iii) To test the hypothesis that drugs that modulate OXPHOS, glycolysis or reactive oxygen species will overcome antiestrogen resistance. I will use our epithelial-stromal coculture models of antiestrogen resistant breast cancer, including the genetically modified cells generated for aim 1 to determine if drugs that metabolically uncouple epithelial and stromal cells can overcome antiestrogen resistance. Specifically, I will test drugs that increase or decrease OXPHOS, inhibit glycolysis or inhibit oxidative stress to determine their effects on carcinoma cell growth. I will also study the functional effects of these drugs in vitro by studying glucose uptake, mitochondrial activity and ROS measurement to ensure expected effects. I will also study the effects of the antioxidant n-acetylcysteine (NAC) on OXPHOS metabolic coupling in humans. Subjects with breast cancer are being enrolled in a pilot clinical trial with NAC where cancer tissue is obtained pre-NAC and post-NAC treatment. The effects of NAC on stromal Caveolin-1 (Cav-1) and MCT4 expression will be studied by IHC. This study and career development plan will allow me to gain the skills to become an independent investigator and the research will discover mechanisms of antiestrogen drug resistance, develop biomarkers and lay the foundations for drug development. I hope to become a physician scientist who links the laboratory and clinical research aspects to improve the lives of patients with breast cancer.